The articles indulge in a bit of exaggeration. Enforcement of sharia law? I wonder if the same argument would be made if Christians handed out gospels at a Hasidic event and got arrested, would said article scream of the specter of Talmudic law? I suspect the cops thought the missionaries were intentionally trying to stir up trouble. This happens quite often to protest groups and whatnot. Just tag 'em, bag 'em and throw some BS charges they'll drop to something minor.
Now, I don't particularly want any religious book to be US law. I like my bacon and idol worship. Should they have been arrested? Nope. But from the video, it's rather clear they're not very favorable towards the people they're attempting to convert (I think the process is called "witnessing", not sure why).
My personal "WTF?" is the wave of people getting arrested for videotaping the police. It's not right by any stretch of the imagination and I really haven't even heard of any attempt at a plausible justification. I agree that the religious folk shouldn't be arrested or detained for handing out any material they wish.